Water damage- screen not turning on

Right, today it rained, and i left my iphone 6s (yes i know its old, but i dont really use it for much and it does the job), in a waterproof bag. Turns out its not so waterproof, and my phone is now pretty broken. The screen was covered in lines before just completely not working anymore. Phone still works as it vibrates when i turn it on, and music was playing from it while the screen turned black (before the battery died).

i literally have no money

anyone know of any cheap ways to repair this